PSI - Issue 64

Patrick Covi et al. / Procedia Structural Integrity 64 (2024) 1774–1781 Patrick Covi and Nicola Tondini/ Structural Integrity Procedia 00 (2019) 000 – 000

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3. Probabilistic analysis results 3.1. FFE framework

The major steps of the FFE probabilistic framework to generate fragility functions are illustrated in Fig. 5 and herein summarized. The procedure begins by defining the structural system's geometry, material properties, and loads. Probabilistic parameters like compartment properties and steel yielding are then generated. Latin Hypercube Sampling is used for the steel retention factor, which was needed to calculate the yield strength at ambient and high temperatures for each simulation. Gravity and seismic analyses are performed using OpenSees, followed by a background MATLAB process that executes the FFE decision algorithm to create fire scenarios based on seismic results. Fire initiation depends on Peak Floor Acceleration (PFA) and Interstory Drift Ratio (IDR) criteria. In detail, the maximum PFA must be greater than or equal to 0.7 g, and the maximum IDR must be greater than or equal to 1% on the same floor in order to start the ignition. Those values are based on the possibility of damage to the gas or electrical services or appliances (Ueno et al., 2004; Scawthorn, 2005; FEMA, 2000). Compartment post-earthquake damages are determined using fragility functions from FEMA P58. The hot gas temperature in compartments is calculated using Ozone, followed by heat transfer analysis and structural analysis at elevated temperatures performed using MATLAB or SAFIR software. Finally, results are utilized to build the fragility functions. Detailed development of the framework is available in two papers (Covi et al., 2023; Covi et al., 2024).

Fig. 5. Comparison between the original and modified accelerogram for the FFE simulation.

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Fig. 6. Deformed shape at the end of the seismic event (magnified by a factor of 5); (b) maximum inter-storey drift (IDR) and maximum peak floor acceleration (PFA); (c) horizontal displacement of the floors.